Information recording and reproducing apparatus and method, and signal decoding circuit for performing timing recovery

• US 20060181797A1
• Filed: 03/24/2006
• Published: 08/17/2006
• Est. Priority Date: 01/21/2002
• Status: Active Grant

• Current Assignee: Toshiba Storage Device Incorporated (Toshiba Corporation)
• Original Assignee: Masaru Sawada, Motomu Takatsu, Takao Sugawara
• Inventors: Sugawara, Takao, Sawada, Masaru, Takatsu, Motomu
• Granted Patent: US 7,515,369 B2
• Time in Patent Office: Days
• US Class Current: 360/51
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs
• CPC Class Codes: G11B 5/09 Digital recording

Abstract

A timing recovery unit detects a phase offset and a frequency offset from a head area of reproduction data and initially corrects them. The timing recovery unit stores data in which a head reproduction signal has been made to be discrete by a fixed clock into a buffer. A phase offset detector detects the phase offset from the data head area in parallel with the operation for writing the data into the buffer. At the same time, a frequency offset detector detects the frequency offset from the data head area in parallel with the operation for writing the data into the buffer. A correction value of the detected phase offset and a correction value of the detected frequency offset are initially set into a digital PLL. While the data is read out from the buffer, a frequency lead-in and a phase lead-in are executed in the head area.

Claims

1. An information recording and reproducing apparatus for recording and reproducing information onto/from a magnetic recording medium, comprising:

a timing recovery unit having an interpolating filter which interpolates a signal oversampled by a fixed clock and down-samples said signal to a symbol rate; and

a phase offset detector which handles a read waveform, as a periodic waveform, in a preamble interval in a sector, detects a phase error between a signal point and a sampling point from a correlation between a reference waveform of said periodic waveform and a sampling waveform, corrects said timing recovery unit by said detected phase error, and allows a loop operation to be started.

2. An apparatus according to claim 1, wherein said timing recovery unit comprises:

an error detector which detects a phase error between the sampling signal of the symbol rate outputted from said interpolating filter and a symbol discrimination signal from a discriminator;

a loop filter which integrates the phase error from said error detector; and

an accumulator which integrates an output of said loop filter and controls coefficients of said interpolating filter so as to eliminate the phase error,

and wherein said accumulator is initialized by said phase error detected by said phase offset detector, thereby allowing a zero phase start to be executed.

3. An information recording and reproducing apparatus for recording and reproducing information onto/from a magnetic recording medium, comprising:

a timing recovery unit having an interpolating filter which interpolates a signal oversampled by a fixed clock and down-samples said signal to a symbol rate; and

a phase offset detector which handles a read waveform, as a periodic waveform, in a preamble interval in a sector, detects a phase error between a signal point and a sampling point from a correlation between a reference signal of said periodic waveform and a sampling signal oversampled for the symbol rate, corrects said timing recovery unit by said detected phase error, and allows an operation to be started.

4. An information recording and reproducing apparatus for recording and reproducing information onto/from a magnetic recording medium, comprising:

a timing recovery unit having an interpolating filter which interpolates a signal oversampled by a fixed clock and down-samples said signal to a symbol rate; and

a frequency offset detector which divides a preamble interval into a plurality of blocks by a length that is integer times as long as a read waveform approximated to a sine wave, obtains a phase error between a sampling waveform and a reference waveform every block, detects a frequency error from a change rate of said phase error of a predetermined number of blocks, corrects said timing recovery unit by said detected frequency error, and allows a loop operation to be started.

5. An apparatus according to claim 4, wherein said timing recovery unit comprises:

an error detector which detects a phase error between the sampling signal of the symbol rate outputted from said interpolating filter and a symbol discrimination signal from a discriminator;

a loop filter which integrates the phase error from said error detector; and

an accumulator which integrates an output of said loop filter and controls coefficients of said interpolating filter so as to eliminate the phase error,

and wherein said loop filter is initialized by said frequency error detected by said frequency offset detector, thereby allowing the loop operation to be started.

6. An information recording and reproducing apparatus for recording and reproducing information onto/from a magnetic recording medium, comprising:

an A/D converter which inputs a read signal of a symbol rate and outputs a sampling signal that was asynchronously oversampled;

an oversampling equalizer which waveform-equalizes said oversampled sampling signal;

a timing recovery unit having an interpolating filter which interpolates said equalization signal and down-samples it to the symbol rate; and

a training circuit which, when a discrimination error between an output signal of said interpolating filter and the symbol rate obtained from a discrimination signal of a discriminator is fed back to training of said oversampling equalizer, inversely interpolates said discrimination error and up-samples it to a signal of a sampling rate.

7. A signal decoding circuit for recording and reproducing information onto/from a magnetic recording medium, comprising:

a timing recovery unit having an interpolating filter which interpolates a signal oversampled by a fixed clock and down-samples said signal to a symbol rate; and

a phase offset detector which handles a read waveform, as a periodic waveform, in a preamble interval in a sector, detects a phase error between a signal point and a sampling point from a correlation between a reference waveform of said periodic waveform and a sampling waveform, corrects said timing recovery unit by said detected phase error, and allows a loop operation to be started.

8. A signal decoding circuit for recording and reproducing information onto/from a magnetic recording medium, comprising:

a timing recovery unit having an interpolating filter which interpolates a signal oversampled by a fixed clock and down-samples said signal to a symbol rate; and

a phase offset detector which handles a read waveform, as a periodic waveform, in a preamble interval in a sector, detects a phase error between a signal point and a sampling point from a correlation between a reference signal of said periodic waveform and a sampling signal oversampled for the symbol rate, corrects said timing recovery unit by said detected phase error, and allows an operation to be started.

9. A signal decoding circuit for recording and reproducing information onto/from a magnetic recording medium, comprising:

a timing recovery unit having an interpolating filter which interpolates a signal oversampled by a fixed clock and down-samples said signal to a symbol rate; and

a frequency offset detector which divides a preamble interval into a plurality of blocks by a length that is integer times as long as a read waveform approximated to a sine wave, obtains a phase error between a sampling waveform and a reference waveform every block, detects a frequency error from a change rate of said phase error of a predetermined number of blocks, corrects said timing recovery unit by said detected frequency error, and allows a loop operation to be started.

10. A signal decoding circuit for recording and reproducing information onto/from a magnetic recording medium, comprising:

an A/D converter which inputs a read signal of a symbol rate and outputs a sampling signal that was asynchronously oversampled;

an oversampling equalizer which waveform-equalizes said oversampled sampling signal;

a timing recovery unit having an interpolating filter which interpolates said equalization signal and down-samples it to the symbol rate; and

a training circuit which, when a discrimination error between an output signal of said interpolating filter and the symbol rate obtained from a discrimination signal of a discriminator is fed back to training of said oversampling equalizer, inversely interpolates said discrimination error and up-samples it to a signal of a sampling rate.

11. An information recording and reproducing method having a timing recovery unit which records and reproduces information onto/from a magnetic recording medium, oversamples a reproduced read signal by a fixed clock, equalizes the signal, thereafter, interpolates the signal, down-samples the signal to a symbol rate, and discriminates it, comprising the steps of:

handling a read waveform, as a periodic waveform, in a preamble interval in a sector and detecting a phase error between a signal point and a sampling point from a correlation between a reference waveform of said periodic waveform and a sampling waveform; and

correcting said timing recovery unit by said detected phase error and allowing a loop operation to be started.

12. An information recording and reproducing method having a timing recovery unit which records and reproduces information onto/from a magnetic recording medium, oversamples a reproduced read signal by a fixed clock, equalizes the signal, thereafter, interpolates the signal, down-samples the signal to a symbol rate, and discriminates it, comprising the steps of:

handling a read waveform, as a periodic waveform, in a preamble interval in a sector and detecting a phase error between a signal point and a sampling point from a correlation between a reference signal of said periodic waveform and a sampling signal oversampled for the symbol rate; and

correcting said timing recovery unit by said detected phase error and allowing an operation to be started.

13. An information recording and reproducing method having a timing recovery unit which records and reproduces information onto/from a magnetic recording medium, oversamples a reproduced read signal by a fixed clock, equalizes the signal, thereafter, interpolates the signal, down-samples the signal to a symbol rate, and discriminates it, comprising the steps of:

dividing a preamble interval into a plurality of blocks by a length that is integer times as long as a read waveform approximated to a sine wave;

obtaining a phase error between a sampling waveform and a reference waveform every block;

detecting a frequency error from a change rate of said phase error of a predetermined number of blocks; and

correcting said timing recovery unit by said detected frequency error and allowing a loop operation to be started.

14. An equalizer training method of an information recording and reproducing apparatus which records and reproduces information onto/from a magnetic recording medium, oversamples a reproduced read signal by a fixed clock, equalizes the signal by an equalizer, thereafter, interpolates the signal by an interpolating filter, down-samples the signal to a symbol rate, and discriminates it, comprising the steps of:

obtaining a discrimination error between said interpolated signal and the symbol rate from a discrimination signal; and

when said discrimination error is fed back to training of said equalizer, inversely interpolating said discrimination error and up-sampling it to a signal of the sampling rate.